Referring to FIG. 1, FIG. 1 is a schematic cross-sectional view showing a conventional LED structure, wherein on a substrate 100, a buffer layer 110 and a n-type confining layer 120 are formed in sequence. An active layer 130, a p-type confining layer 140, a transparent electrode layer 150 and a p-type electrode pad 160 are formed on one portion of the n-type confining layer 120, and a n-type electrode pad 170 is formed on the other portion of the n-type confining layer 120. The n-type electrode pad 170 is spaced from a light-emitting epitaxial structure 180 by a predetermined gap d, wherein the light-emitting epitaxial structure 180 is composed of the active layer 130, the p-type confining layer 140 and the transparent electrode layer 150.
After a LED structure is formed, it is desirable to perform the subsequent processes of die bonding and wire bonding. The die bonding or wire bonding process mainly uses an image comparison and recognition method to select a LED chip matching a predetermined reference image. At this point, in the conventional LED structure, due to the etching process, the surface roughness of the epitaxial layers (the p-type confining layer 140 and the transparent electrode layer 150) under the p-type electrode pad 160 is different from that of the epitaxial layers (the n-type confining layer 120) under the n-type electrode pad 170, and thus the light scattering and reflected intensities of the p-type electrode pad 160 are inconsistent with those of the n-type electrode pad 170, thus lowering the image recognition rate, leading to the increase of downtime ratio, further causing the occurrence of abnormalities or the decrease of production, and resulting in rough surface textures.
The conventional skill adopts the method of adjusting etch parameters to make the surface roughnesses of the epitaxial layers under these two electrode pads as similar as possible. However, the respective conditions are different for each product lot, so that the conventional method of adjusting the etch parameters is significantly limited and it is difficult to make the surface roughnesses of the epitaxial layers under these two electrode pads reach the same level, thus causing recognition difficulty in the processes of die bonding and wire bonding. Moreover, this conventional skill has to adjust the etch parameter for each individual product lot, and thus is not suitable for use in mass production.